I installed 5.1, only to notice it's unusable since I use synchronization a lot and there is known bug that it hangs after closing sync (Bug 915).

What gripes me most is that according to change log it's fixed already, just not released. I suggest you release 5.1.1 and start to collecting stuff to 5.1.2, that sync bug is real showstopper for me at least.

I think it's appropriate to release often especially when you just changed major version number, people expect it to be buggy after major change, but they also expect those crash / hang bugs to be fixed fast.

I would not like to install 4.x again just to be able to sync, since I like a lot all of the new features in 5.1. Great work nonetheless.

5.1: Commander: also noticed that sporadically even if I'm not syncing the Local Browsers ceases to function after uploading. (Same way after syncing) Must restart the WinSCP to get browsing in local browser working.